Il 30/08/22 07:57, Luca ha scritto:
Il 28/08/22 15:13, Samuel Thibault ha scritto:
+ }
+ else
+ {
+ size_t n = size / 8;
+ saddr += n*number;
+ usize += n*number;
+ align_inline(saddr, 4);
+ align_inline(usize, 4);
This should be alignof(some_align_type)
Will do.
Thinking about it, I'm not sure about alignof(). For example, if I add
something like
#define MACH_MSG_ALIGNMENT alignof(rpc_vm_offset_t)
then I'm assuming that the alignment of a data type with a given size is
the same on 32-bit and 64-bit variants. While this is true on x86 up to
4-byte size, it's not true for 8-byte size. Specifically, on 32-bit this
would be
#define MACH_MSG_ALIGNMENT alignof(unsigned long)
while on 64-bit it would be
#define MACH_MSG_ALIGNMENT alignof(unsigned int)
Currently the copy_user.c file is only compiled on 64-bit, but I suppose
this definition would be useful in other places, not 64-bit specific,
and also in mig (and also if one day gnumach supports non-x86 :))
For me it would be less confusing to just define it as 4. As far as I
understand it's the default alignment of structure fields on the 32-bit
variant (from how mig works), and it seems a bit "forced" to try to
derive this value on a 64-bit variant. By the way, the rpc code
generated by mig now forces this alignment, so the reason to have it
seems mostly backwards compatibility.
Luca
